Genetic and T2 biomarkers linked to the efficacy of HDM sublingual immunotherapy in asthma.

BACKGROUND: Hypersensitivity to house dust mite (HDM) allergens is a common cause of allergic asthma symptoms and can be effectively treated with allergy immunotherapy (AIT). OBJECTIVE: To investigate whether genetic and type 2 (T2) inflammatory biomarkers correlate with disease severity in subjects with allergic asthma, and whether this can be modified by AIT. METHODS: MITRA (NCT01433523) was a phase III, randomised, double-blind, placebo-controlled trial of HDM sublingual immunotherapy (SLIT)-tablets in adults with HDM allergic asthma. Post hoc analyses of the study population (N=742) evaluated associations between T2 inflammatory (blood eosinophils, eosinophil cationic protein (ECP), total IgE and tryptase) and genetic (single-nucleotide polymorphisms, SNP) biomarkers (n=582) for the primary study endpoint (time to first moderate/severe asthma exacerbation). SNP associations were verified in HDM-positive subgroup from an independent 3-year Severe Asthma Research Programme (SARP3) subject cohort. RESULTS: An increased asthma exacerbation risk in subjects homozygous for SNP rs7216389 (chromosomal locus 17q12-21) was reduced (p=0.037) by treatment with HDM SLIT (HR=0.37 (95% CI 0.22 to 0.64), p<0.001). The associations between exacerbation risk and 17q12-21 SNPs were replicated in the SARP3 HDM-positive subgroup. High levels of T2 biomarkers were associated with increased risk of asthma exacerbations in the placebo group. HDM SLIT-tablet treatment reduced this risk (blood eosinophils: HR=0.50 (95% CI 0.30 to 0.85); ECP: HR=0.45 (95% CI 0.29 to 0.87); tryptase: HR=0.45 (95% CI 0.25 to 0.80)). The treatment effect was higher (p=0.006) for subjects with a higher number of elevated T2 biomarkers. CONCLUSIONS: HDM SLIT-tablet AIT is efficacious in HDM-sensitised asthma subjects with a genetic asthma predisposition and/or an underlying T2 endotype. TRIAL REGISTRATION NUMBER: NCT01433523.

Smoking and tetramer tryptase accelerate intervertebral disc degeneration by inducing METTL14-mediated DIXDC1 m6 modification.

Although cigarette smoking (CS) and low back pain (LBP) are common worldwide, their correlations and the mechanisms of action remain unclear. We have shown that excessive activation of mast cells (MCs) and their proteases play key roles in CS-associated diseases, like asthma, chronic obstructive pulmonary disease (COPD), blood coagulation, and lung cancer. Previous studies have also shown that MCs and their proteases induce degenerative musculoskeletal disease. By using a custom-designed smoke-exposure mouse system, we demonstrated that CS results in intervertebral disc (IVD) degeneration and release of MC-restricted tetramer tryptases (TTs) in the IVDs. TTs were found to regulate the expression of methyltransferase 14 (METTL14) at the epigenetic level by inducing N6-methyladenosine (m6A) deposition in the 3' untranslated region (UTR) of the transcript that encodes dishevelled-axin (DIX) domain-containing 1 (DIXDC1). That reaction increases the mRNA stability and expression of Dixdc1. DIXDC1 functionally interacts with disrupted in schizophrenia 1 (DISC1) to accelerate the degeneration and senescence of nucleus pulposus (NP) cells by activating a canonical Wnt pathway. Our study demonstrates the association between CS, MC-derived TTs, and LBP. These findings raise the possibility that METTL14-medicated DIXDC1 m6A modification could serve as a potential therapeutic target to block the development of degeneration of the NP in LBP patients.

Mast cell activation: beyond histamine and tryptase.

INTRODUCTION: Mast cells are found in all tissues and express numerous surface receptors allowing them to sense and respond to allergic, autoimmune, environmental, neurohormonal, pathogenic and stress triggers. Stimulated mast cells are typically called 'activated' but the mechanisms involved and the mediators released can vary considerably. Mast cell activation diseases (MCADs) include primary, secondary and idiopathic conditions, especially mast cell activation syndrome (MCAS), but mast cells are activated in many other disorders making the diagnosis and treatment challenging. AREAS COVERED: Mast cells can release numerous biologically active mediators, some of which are prestored in secretory granules while others are newly synthesized and released without degranulation. Most of the emphasis has so far been on secretion of histamine and tryptase, which do not explain all the multisystemic symptoms experienced by patients with MCADs. As a result, drug development has focused on antiproliferative therapy or blocking the action of individual mediators and not on inhibitors of mast cell activation. EXPERT OPINION: Activated mast cells are involved in the pathogenesis of MCADs, but also in other disorders making appropriate diagnosis and treatment challenging. The definition of mast cell activation should be expanded beyond histamine and tryptase, with an emphasis on better detection and treatments.

Aerosol-Administered Adelmidrol Attenuates Lung Inflammation in a Murine Model of Acute Lung Injury.

Acute lung injury (ALI) is a common and devastating clinical disorder with a high mortality rate and no specific therapy. The pathophysiology of ALI is characterized by increased alveolar/capillary permeability, lung inflammation, oxidative stress and structural damage to lung tissues, which can progress to acute respiratory distress syndrome (ARDS). Adelmidrol (ADM), an analogue of palmitoylethanolamide (PEA), is known for its anti-inflammatory and antioxidant functions, which are mainly due to down-modulating mast cells (MCs) and promoting endogenous antioxidant defense. The aim of this study is to evaluate the protective effects of ADM in a mice model of ALI, induced by intratracheal administration of lipopolysaccharide (LPS) at the dose of 5 mg/kg. ADM 2% was administered by aerosol 1 and 6 h after LPS instillation. In this study, we clearly demonstrated that ADM reduced lung damage and airway infiltration induced by LPS instillation. At the same time, ADM counteracted the increase in MC number and the expression of specific markers of MC activation, i.e., chymase and tryptase. Moreover, ADM reduced oxidative stress by upregulating antioxidant enzymes as well as modulating the Nf-kB pathway and the resulting pro-inflammatory cytokine release. These results suggest that ADM could be a potential candidate in the management of ALI.

Probiotics in Experimental Ulcerative Colitis: Mast Cell Density and Neuronal Hypertrophy.

BACKGROUND: Probiotics such as Lactobacillus and Bifidobacterium are among the supportive treatment methods to achieve effective results in ulcerative colitis. This study was established to investigate the effect of probiotics in experimental ulcerative colitis and to detect changes in mast cell and neuronal structures in this treatment method. METHODS: A total of 48 adult male rats were used to study the effects of probiotics on ulcerative colitis. The animals were divided into 6 groups as control, experimental colitis, and four probiotic protective groups. Three different bacterial strains were administered to the protective groups individually and in combination by gavage. PGP 9.5 antibody and mast cell tryptase were used for the detection of neuronal structures and mast cells. The number of Schwann cells and ganglia, size measurements of ganglia, and density of mast cells were evaluated. RESULTS: Compared to the control, an increase in the number of mast cells was detected in all groups. Especially the increase in the num- ber of mast cells was found to be statistically significant in combined probiotic administration. In the detection of neuronal structures, a significant increase in the number of Schwann cells and ganglia was detected in groups where probiotics were administered combined and individually. CONCLUSION: These results suggest that probiotics may play a role in the supporting effect of increasing the number of mast cells and neuronal structures, protecting the intestinal wall. We think that more specific and detailed studies should be conducted to evaluate the protective/therapeutic effect of probiotics in future studies.

Efficacy of avapritinib versus best available therapy in the treatment of advanced systemic mastocytosis.

Advanced systemic mastocytosis (AdvSM) is a rare myeloid neoplasm associated with poor overall survival (OS). This study (NCT04695431) compared clinical outcomes between patients with AdvSM treated with avapritinib in the Phase 1 EXPLORER (NCT0256198) and Phase 2 PATHFINDER (NCT03580655) trials (N = 176) and patients treated with best available therapy (BAT; N = 141). A multi-center, observational, retrospective chart review study was conducted at six study sites (four European, two American) to collect data from patients with AdvSM who received BAT; these data were pooled with data from EXPLORER and PATHFINDER. Comparisons between outcomes of OS, duration of treatment (DOT), and maximum reduction in serum tryptase were conducted between the treatment cohorts, with adjustment for key covariates. The results indicated that the avapritinib cohort had significantly better survival (adjusted hazard ratio (HR) (95% confidence interval (CI)): 0.48 (0.29, 0.79); p = 0.004) and significantly longer DOT (HR: 0.36 (0.26, 0.51); p < 0.001) compared to the BAT cohort. Additionally, the mean difference in percentage maximum reduction in serum tryptase levels was 60.3% greater in the avapritinib cohort (95% CI: -72.8, -47.9; p < 0.001). With no randomized controlled trials comparing avapritinib to BAT, these data offer crucial insights into the improved efficacy of avapritinib for the treatment of AdvSM.

Mast Cell-Derived Proteases Induce Endothelial Permeability and Vascular Damage in Severe Fever with Thrombocytopenia Syndrome.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging hemorrhagic fever acquired by tick bites. Whether mast cells (MCs), the body's first line of defense against pathogens, might influence immunity or pathogenesis during SFTS virus (SFTSV) infection remained unknown. Here, we found that SFTSV can cause MC infection and degranulation, resulting in the release of the vasoactive mediators, chymase, and tryptase, which can directly act on endothelial cells, break the tight junctions of endothelial cells and threaten the integrity of the microvascular barrier, leading to microvascular hyperpermeability in human microvascular endothelial cells. Local activation of MCs (degranulation) and MC-specific proteases-facilitated endothelial damage were observed in mouse models. When MC-specific proteases were injected subcutaneously into the back skin of mice, signs of capillary leakage were observed in a dose-dependent manner. MC-specific proteases, chymase, and tryptase were tested in the serum collected at the acute phase of SFTS patients, with the higher level significantly correlated with fatal outcomes. By performing receiver operator characteristic curve (ROC) analysis, chymase was determined as a biomarker with the area under the curve value of 0.830 (95% CI = 0.745 to 0.915) for predicting fatal outcomes in SFTS. Our findings highlight the importance of MCs in SFTSV-induced disease progression and outcome. An emerging role for MCs in the clinical prognosis and blocking MC activation as a potential drug target during SFTSV infection was proposed. IMPORTANCE We revealed a pathogenic role for MCs in response to SFTSV infection. The study also identifies potential biomarkers that could differentiate patients at risk of a fatal outcome for SFTS, as well as novel therapeutic targets for the clinical management of SFTS. These findings might shed light on an emerging role for MCs as a potential drug target during infection of other viral hemorrhagic fever diseases with similar host pathology as SFTS.

Dose-dependent inactivation of airway tryptase with a novel dissociating anti-tryptase antibody (MTPS9579A) in healthy participants: A randomized trial.

Tryptase is the most abundant secretory granule protein in human lung mast cells and plays an important role in asthma pathogenesis. MTPS9579A is a novel monoclonal antibody that selectively inhibits tryptase activity by dissociating active tetramers into inactive monomers. The safety, tolerability, pharmacokinetics (PKs), and systemic and airway pharmacodynamics (PDs) of MTPS9579A were assessed in healthy participants. In this phase I single-center, randomized, observer-blinded, and placebo-controlled study, single and multiple ascending doses of MTPS9579A were administered subcutaneously (s.c.) or intravenously (i.v.) in healthy participants. In addition to monitoring safety and tolerability, the concentrations of MTPS9579A, total tryptase, and active tryptase were quantified. This study included 106 healthy participants (82 on active treatment). Overall, MTPS9579A was well-tolerated with no serious or severe adverse events. Serum MTPS9579A showed a dose-proportional increase in maximum serum concentration (Cmax ) values at high doses, and a nonlinear increase in area under the curve (AUC) values at low concentrations consistent with target-mediated clearance were observed. Rapid and dose-dependent reduction in nasosorption active tryptase was observed postdose, confirming activity and the PK/PD relationship of MTPS9579A in the airway. A novel biomarker assay was used to demonstrate for the first time that an investigative antibody therapeutic (MTPS9579A) can inhibit tryptase activity in the upper airway. A favorable safety and tolerability profile supports further assessment of MTPS9579A in asthma. Understanding the exposure-response relationships using the novel PD biomarker will help inform clinical development, such as dose selection or defining patient subgroups.

Mast cell protease 6 is required for allograft tolerance.

It has been shown that mast cells (MC) are absolutely required for transplant acceptance. However, only a few of the numerous mediators produced by MC have been proposed as potential mechanisms for the observed immunosuppression. The role of proteases in acquired immune tolerance as such has not yet been addressed. In this study, we have shown the requirement for MC protease 6 (MCP6), an MC-specific tryptase, to establish tolerance toward an allogeneic skin graft. The substrate for MCP6 is interleukin (IL)-6, cytokine generally considered to indicate transplant rejection. Herein we have shown an inverse correlation between MCP6 and IL-6. High expression of MCP6 is accompanied by low levels of IL-6 when the allograft is accepted, whereas low expression of MCP6 in combination with high levels of IL-6 are observed in rejecting grafts. Moreover, tolerance toward an allogeneic graft cannot be induced in MCP6(-/-) mice. Rejection observed in these mice was comparable to that of MC-deficient hosts; it is T-cell mediated. These findings suggest that MCP6 actively depletes the local environment of IL-6 to maintain tolerance.